Broadband antenna

Abstract

The present invention relates to an antenna comprising:

Description

BRIEF DESCRIPTION OF THE DRAWING

The invention can be better understood on reading the following detailed description of non-limiting embodiments of the invention and on examining the accompanying drawing, in which:

FIG. 1 is a diagrammatic fragmentary view of an antenna with a dipole radiating element and in accordance with the invention;

FIG. 2 is a diagrammatic plan view of the FIG. 1 antenna;

FIG. 3 is a diagrammatic and fragmentary view showing the conductive sheet used for forming the outer element of the FIG. 1 antenna;

FIGS. 4 to 7 are diagrammatic and fragmentary views showing other examples of sheets that can be used to form the outer element of the antenna of the invention; and

FIG. 8 is a diagrammatic and fragmentary view of a monopole antenna constituting an embodiment of the invention.

MORE DETAILED DESCRIPTION

FIG. 1 shows a so-called “continuous profile” antenna 1 comprising a central radiating element 2 of the dipole type having a longitudinal axis X, and an outer element 3 drawn in dashed lines and that can be said to be partially parasitic, surrounding the radiating element 2.

The antenna 1 shown has a dielectric material 4 in which the radiating element 2 and the outer element 3 are embedded, at least in part.

In a variant, the radiating element 2 and the outer element 3 may be separated by air.

The radiating element 2 may be of any type, for example a printed or cylindrical dipole, and it is may be in the form of a rod.

The outer element 3 can be considered as being an adaptive load, and it is not connected to any ground.

In the example shown, the outer element 3 is formed by a rolled-up electrically conductive sheet 5 that has the shape of an isosceles triangle, as shown in FIG. 3. In a variant, the shape of the triangle may be arbitrary.

The sheet 5 may be rolled in a spiral, for example a variable-pitch spiral, as can be seen in FIG. 2.

The maximum height H of the outer element 3 measured along the axis X corresponds to the length H of the base of the isosceles triangle of the sheet 5.

In the example described, the outer element 3 presents a minimum height along the roll axis that is zero, corresponding to the vertex H of the isosceles triangle opposite from its base.

The antenna 1 may be of the type presenting an ultra-broad band.

The outer element 3 may present other shapes.

For example, as shown in FIG. 4, the outer element 3 may be made from a conductive sheet 5 in the shape of a right-angled triangle.

In a variant, the conductive sheet 5 may be in the form of a truncated right-angled triangle, so that the outer element 3 presents a minimum height along the roll axis that is not zero.

In a variant, as shown in FIG. 6, the conductive sheet 5 may have two sides that are perpendicular and a third side of a shape that is curvilinear, being of the decreasing exponential type.

As shown in FIG. 7, the conductive sheet 5 may have a side that is formed by a succession of crenellations, with the height of the outer element varying along the roll, alternately increasing and decreasing.

FIG. 8 shows an antenna 10 of the so-called “matching sleeve” type constituting another embodiment of the invention.

This antenna 10 is of the monopole type, and comprises a central radiating element 11, an outer element 12 rolled around the radiating element 11, and a ground element 13 to which the outer element 12 is connected. The outer element may be made integrally with the ground element.

The elements 11 and 12 may be made of conductive material, or in a variant they may be made using printed circuit cards.

In another variant, the radiating element 11 may be of the dipole type.

The outer element 12 may be considered as an extension of the ground element 13.

In the example described, the outer element 12 is constituted by rolling up a sheet that has the shape of a right-angled triangle.

Naturally, the outer element 12 may present one of the other shapes described above.

The antenna 10 makes it possible to obtain a bandwidth that is ultra-broad.

The influence of the ground element 13 on the operation of the antenna can be made to be very small by means of the invention.

The radiating element 11 may be a single piece or it may be assembled from a plurality of elements.

In the examples shown, the central radiating element and the outer element are concentric.

In a variant, the central radiating element could be off-center relative to the outer element.

Although the present invention herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the present invention. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims.

Claims

1. An antenna comprising: at least one central longitudinal radiating element; andat least one outer element comprising at least one rolled-up electrically-conductive sheet disposed around the central element, without electrical contact therebetween, wherein the outer element presents a height that is strictly decreasing, or alternatively that increases and decreases along the roll.

2. An antenna according to claim 1, wherein the conductive sheet possesses a first side defining a maximum height of the outer element, and a second side, in particular a side perpendicular to the first, defining a base of the outer element.

3. An antenna according to claim 2, wherein the conductive sheet presents the shape of a right-angled triangle.

4. An antenna according to claim 2, wherein the conductive sheet has a third side interconnecting the first two sides and presenting the shape of a decreasing exponential.

5. An antenna according to claim 2, wherein the conductive sheet has a third side interconnecting the first and second sides and formed by a succession of crenellations.

6. An antenna according to claim 1, wherein the minimum height of the outer element is not zero.

7. An antenna according to claim 1, wherein the outer element comprises a rolled-up conductive sheet having the shape of an isosceles triangle with its base defining the maximum height of the outer element.

8. An antenna according to claim 1, wherein the outer element is rolled in a spiral, in particular a variable-pitch spiral.

9. An antenna according to claim 1, wherein the outer element is arranged to operate without contacting ground.

10. An antenna according to claim 9, wherein the central radiating element is a dipole.

11. An antenna according to claim 1, wherein the outer element is arranged to operate in contact with ground.

12. An antenna according to claim 11, wherein the central radiating element is a monopole.

13. An antenna according to claim 1, including a dielectric material surrounding the central radiating element and the outer element.